LOHAN, the nightclub, is opening this weekend in Athens ... and we're told it's all thanks to LiLo's pal, Dennis Papageorgiou. The Greek restaurateur is the owner, but we're told Lindsay's getting a big chunk of the profits, aka ... back end.

A LOHAN spokesperson tells us Dennis came up with the idea in July -- the same month Lindsay and ex-fiance Egor split -- and Lindsay was down with it, naturally.

We're told the decor is "abandoned factory" chic with baroque detailing, whatever that means. Best of all ... there's a standard VIP area, and also a completely secluded VVIP area. That's not a joke. Think Lindsay meets 'Night at the Roxbury.'